Hong Kong authorities are considering lowering the threshold for activating higher-tier heat-stress warnings during exceptionally hot weather , following public criticism that the alert was not upgraded even as the city sweltered through its hottest day on record. Hui said the heat stress at work warning system took into account factors such as air temperature, humidity, wind speed and solar radiation, but that their weighting had been “localised” to suit Hong Kong’s climate. “In Hong Kong, the heat stress does not always track actual temperature change. “Our system is more sensitive to this muggy situation, and the weighting of direct solar radiation is relatively smaller.” The Labour Department came under criticism after its Heat Stress at Work Warning System remained at the lowest level while the city’s forecaster recorded a scorching 36.9 degrees Celsius (103 Fahrenheit) on Sunday afternoon – the highest temperature since records began in 1884.